These studies are concerned with the development of mycoplasma genetics and the description of the molecular events in the replication of the subcellular organelles of Mycoplasma gallisepticum and their ordering prior to cell division. Studies of an Acholeplasma laidlawii replication deficient variant will examine whether this mutation involves loss of one of the mycoplasma DNA repair systems, which have been previously described as part of this project. A more detailed biochemical and biophysical characterization of mycoplasma folded chromosomes will be carried out. The molecular basis of the effect of cytochalasin B on mycoplasmas will be examined. Studies of the evolutionary conservation of mycoplasma rRNA oligmers will be continued. BIBLIOGRAPHIC REFERENCES: Maniloff, J. and D. C. Quinian (1974). Partial purification of a membrane-associated deoxyribonucleic acid complex from Mycoplasma gallisepticum. J. Bacteriol. 120:495-501. Maniloff, J. (1975). Thermodynamic considerations of the deoxyribonucleic acid helix-cruciform transition. J. Theoret. Biol. 53:497-501.